... as over-current,over-voltage,over-temperature,overload,DC and so on.so the series have 2 defferent uses.SPECIFICATIONS:MODELCQ-100CQ ... .)20KΩ/10KΩProtectionOverheat,short ciruits,DC,limit and softstart,Output Relay -Zero CurrentSwitch,Intellectual Clip LimiterCrosstalk70dB70dB70dB Power Amplifier CQ ...